1. Field of the Invention
The present invention generally relates to a radio communication technical field, and, in particular, to a radio receiver, a radio transmitter and impedance control method for performing radio communication with the use of a plurality of antenna elements.
2. Description of the Related Art
As a technology especially taking into an attention for such a technical field, a so-called multi-input multi-output (MIMO) communication system is known. This system has been developed for improving transmission rate per capacity, i.e., per frequency (bps/Hz) by preparing a plurality of antenna elements at each of a transmission end and a reception end, and simultaneously transmitting different signals for the respective antenna elements within a common frequency band. The above-mentioned capacity is also called throughput. For example, European Patent Application Publication No. 1233565 and G. J. Foschini, et al., ‘Simplified Processing for High Spectral Efficiency Wireless Communication Employing Multi-Element Arrays’, IEEE Journal on Selected Areas in Communications, Vol. 17, No. 11, pp. 1841–1852, November 1999 disclose communication methods of the MIMO system. Also, numerical expressions or such for the throughput (capacity) achieved by the MIMO system is disclosed by Sirikiat Lek Ariyavisitakul, ‘Turbo Space-Time Processing to Improve Wireless Cannel Capacity’, IEEE Trans. on Commun, vol. 48, no. 8, August 2000.